Surface-enhanced Raman spectroscopy (SERS) was used for detecting Rhodamine B (RB) which is often added illegally to chili powder. Based on density functional theory, the Raman spectrum of RB was calculated and characteristic peaks of RB were assigned to the corresponding vibrational modes. RB was detected utilizing paper-based SERS substrates which were fabricated via a liquid–liquid interface-mediated self-assembly technique. Meanwhile, with simple sample pretreatment, the detection limit could reach 10−6 g g−1 for RB in chili powder (5 × 10−7 g mL−1 in extraction agent). Within the concentration range from 10−2 g g−1 to 10−6 g g−1, Raman intensity follows a certain function in relation to the concentration of RB. The recovery of this method ranges from 96.4% to 108.9%, which gives rapid and reliable quantitative detection of RB in chili powder. Therefore, the proposed SERS method is suitable for on-site detection and analysis of RB in chili powder.
